Automatic speed control and programming system for high-speed belt conveyor type throwers

ABSTRACT

An apparatus for the controlled feeding of charge material into a metallurgical reactor or vessel is constructed and designed to distribute charge material over the surface of a molten bath in the vessel in a substantially uniform layer and in a manner to obtain high rates of efficiency in smelting and converting. An endless belt thrower is provided which is constructed and dimensioned to convey the material and feed it into the vessel in a predetermined manner. A variable speed motor is adapted to drive the thrower and a control system is adapted to regulate the voltage of the motor and the speed at which the motor drives the thrower. A program system is adapted to regulate the control system according to a predetermined program.

. United States Patent 1191 Kitzinger et al.

1451 Jan. 15,1974

[ AUTOMATIC SPEED CONTROL AND 2,011,284 8/1935 Hunt 214/1822 x PROGRAMMING SYSTEM FOR 2,834,484 5/1958 Devaney et a1... 214/18 R HIGILSPEED BELT CONVEYOR TYPE gig-$11223! al 198/112 THROWERS 2,812,052 11/1957 Doyer 198/128 [75] Inventors: Frank Kitzinger, Montreal; Peter i g g Ormeaux Quebec both Primary ExaminerRobert G. Sheridan 0 am a Attorney-Fleit, Gipple & Jacobson [73] Assignee: Noranda Mines Limited, Montreal, Quebec, Canada 22 Filed: June 9, 1971 [57] ABSTRACT PP 151,193 An apparatus for the controlled feeding of charge material into a metallurgical reactor or vessel is constructed and designed to distribute charge material [30] Foreign Apphcamm Pnomy Data over the surface of a molten bath in the vessel in a M31. 5, l97l Canada 106971 substantially uniform layer and in a manner to obtain 4 high rates of efficiency in smelting and converting. An [52] Cl 214/1822 198/110 endless belt thrower is provided which is constructed 198/ 128 and dimensioned to convey the material and feed it [5 llft. Clinto the vessel in a predetermined manner A variable [58] Field of Search 214/1822, 18.24, Speed motor is adapted to drive the thrower and a 214/1826 1836 17 17 control system is adapted to regulate the voltage of l 128 the motor and the speed at which the motor drives the thrower. A program system is adapted to regulate the [56] References cued control system according to a predetermined program,

UNITED STATES PATENTS 2,657,990 11/1953 Kuz ell 198/128 X 17 Claims, 5 Drawing Figures q THROWER f' HELD 2353c.

MOTOR 2 mwERs'rAT MOTORARM 3 I I I Pi i y 41/7422 1;

11mm DIFFERENTTAL -'WLTAGE RELAY SUPPLY 1 1 PROGRAM REFERENCE VOLTAGE Pgggg o/ r SUPPLY PATENTEDJAN 1 5 mm AUTOMATIC SPEED CONTROL AND PROGRAMMING SYSTEM FOR HIGH-SPEED BELT CONVEYOR TYPE THROWERS This invention relates broadly to the automatic control of conveyors. More particularly, this invention relates to a system for controlling and programming the speed of high-speed belt conveyors, such as slingers, or throwers, which are used to charge metallurgical furnaces or roasters, or to load and stockpile bulk materials.

In charging or feeding some types of metallurgical furnaces it is desirable to spread the charge material over a wide area of the surface of the molten bath, one objective being to obtain high smelting rates. In reverberatory furnaces used to produce copper matte this practice is referred to as bath smelting. One method of feeding reverberatory furnaces for bath smelting is taught by Kuzzel, US. Pat. No. 2,657,990 and also Canadian Pat. No. 527,977.

In the continuous smelting and converting of copper concentrates to metallic copper as is taught, for example, by Themelis and Tarassoff in Canadian Pat. No. 833,475 and by Themelis and McKerrow in Canadian Application No. 104,1 1 l filed Feb. 1, 1971, high smelting rates are achieved by charging copper concentrate pellets in such a manner that a large surface area of the bath is covered with a thin layer of pellets, or pellets and flux.

One form of charging device suitable for feeding a furnace in accordance with the method of Kuzell, and also that of Themelis andTarassoff, involves a short high-speed belt conveyor consisting of an endless belt driven by a motor and supported by a tail or drive pulley and also a head or front pulley, with a flanged pulley, and a flanged hold-down roller or the like forming a concave curve in the belt between the head pulley and the tail pulley. This device also has a spout directing material from a hopper or chute onto the concave curved portion of the belt whereby the material is urged against the belt by centrifugal force and is propelled in a stream from the belt as the belt passes over the front pulley. Such devices are variously called slinger belts, slingers, and throwers, but hereinafter will be referred to as throwers.

- Throwers also have many other uses. They may be used to feed concentrates into fluid bed roasters. Very commonly they are used to stockpile free-flowing bulk materials, to load them into ships, railway boxcars, and trucks, and generally to assist in moving materials from one location to another.

Commonly, throwers are provided with constant speed motors and for a fixed position of the thrower, the distance that the stream of bulk material is propelled is governed by the trajectory of the stream leaving the belt, and may be varied within limits by raising or lowering the front pulley, for example, by tilting or rotating the thrower about a horizontal axis by means of trunnions. Constant speed throwers can be suspended or mounted so that the direction of the propelled material can be changed by turning the thrower about a vertical axis. For a fixed thrower position, trajectory, and belt speed, the propelled material forms a conical shaped pile.

It has been found advantageous in some arrangements to provide variable speed motors for throwers, particularly in feeding metallurgical furnaces, so that the trajectory of the propelled material can be varied by regulating the belt speed.

Where it is desirable to spread the propelled material, as in feeding metallurgical furnaces, it is necessary to vary from time to time both the direction of the propelled stream of material and its trajectory. In the practice of bath smelting in a copper reverberatory furnace according to the teaching of Kuzell, an operator attempts to keep a layer of feed material spread on the surface of the bath by manually adjusting the belt speed of the thrower or the elevation of the front pulley, and the lateral position of the thrower. However, this has the disadvantage that the spread of the charge depends on the judgment and response time of the operator, and a repetitive and reproducible charging pattern is thus not easily achieved.

In the continuous smelting and converting of copper concentrates a repetitive and reproducible charging pattern is desirable. Moreover, as automation is becoming a significant objective in continuous processing, dependence on an operator in such a key part of the process as charging should preferably be avoided.

This invention, therefore, provides a system automatically to regulate and program the speed of a thrower, whereby in a continuous smelting and converting apparatus for copper concentrates and also in other metallurgical furnaces, particularly in practising bath smelting in a copper reverberatory furnace, the charge is continuously spread on the surface of the molten bath according to a predetermined charge distribution pattern.

This invention also provides a system automatically to regulate and program the speed of a thrower whereby a bulk material is distributed onto a stockpile in a predetermined manner.

According to the present invention a method and apparatus for the controlled feeding of material into a vessel includes, an endless belt thrower constructed and dimensioned to convey said material and feed it into said vessel in a predetermined manner, a variable speed motor adapted to drive said thrower, a control system adapted to regulate the voltage of said motor and the speed at which said motor drives said thrower and a program system adapted to regulate said control system according to a predetermined program.

One embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which:

FIG. 1 is a block diagram of the thrower control systern.

FIG. 2 is a schematic distribution profile along the line of throw, showing the effect of different belt speeds.

FIG. 3 is a schematic material distribution contour plot obtained with a programmed belt speed.

FIG. 4 is a schematic contour plot of charge distribution obtained with an oscillating thrower.

FIG. 5 is a circuit diagram of the thrower speed control.

With reference to FIG. 1 the automatic speed control and programming system of the present invention has a thrower l which is driven by a variable speed d.c. motor 2. DC. current is supplied to the motor by two rectifiers l0 and 11. Rectifier I0 is in the armature circuit 13, and rectifier II is in the field circuit 14. The motor speed is regulated by a powerstat 3 driven by a servomotor 4 in the a.c. side of the armature circuit.

The program system is made up of four major components which include a program timer 9, a differential relay 6, and two reference voltage supplies, 7 and 8. Feedback to the control is provided by a tachometer generator 5 connected to a shaft of the thrower motor 2, in the form of a voltage which is a linear function of the motor speed and the belt speed of the thrower. The differential relay 6 then drives the powerstat 3 by servomotor 4, in the appropriate direction to cause the motor to either speed up or slow down, thereby also causing the tachometer generator voltage to increase or decrease. When the voltage of the tachometer generator 5 and the activated reference voltage supply 7 or 8 are balanced, the differential relay stops the servomotor.

In operation, the thrower belt speed passes through a continuous series of cycles each made up of an accelerate period, a delay period, and a decelerate period. This sequence of periods is controlled by the program timer.

During the accelerate period the timer 9 connects the differential relay to reference voltage supply 8, the output of which is set to correspond to the tachometer generator voltage which would be generated at the desired high belt speed limit. As indicated, the powerstat 3 is driven by the servomotor 4 to accelerate the thrower 1. When the belt speed reaches the pre-set high speed limit the servomotor 4 ceases to increase the voltage on powerstat 3 and accordingly the motor 2 ceases acceleration. The timer 9 receives an impulse signal and starts a delay period in which the servomotor 4 remains inactive and the thrower l continues to operate at the pre-set high speed. The length of the period is pre-set to the desired value.

At the end of the delay period, the timer 9 automatically switches the differential relay 6 to reference voltage supply 7 and the servomotor 4 starts decreasing the voltage on powerstat 3 and thus decreases the speed of the motor 2. When the speed decreases to the pre-set low speed limit the timer 9 receives an impulse, and a new cycle is started with an accelerate period.

A time delay at the high speed is required because, at high speed, the material is distributed over a large elliptical area as compared to a smaller circular area at low speeds. The charging rate per unit area therefore decreases when the thrower operates at high speed spreading the material over a larger area. By retaining the high speed for a controlled period of time a more even distribution is provided. A second delay period may be introduced while the thrower operates at the pre-set low speed, but this will depend on the feed requirements of the operation. Although a second delay period is unnecessary to obtain uniform charge distribution, it may be desirable in some cases to provide a higher charging rate in an area of the molten bath nearest the thrower. For example in the reactor described in Canadian Pat. Application No. 104,] l l filed on Feb. 1, 1971 in the names of Themelis and McKerrow it may be desirable to provide a high charging rate of copper concentrate in the turbulent area around the tuyeres.

As indicated FIG. 4 is a schematic contour plot of charge distribution obtained with an oscillating thrower. The charge distribution areas are shown by way of example by the different cross-hatched sections. The feeding rates in terms of pounds per square feet per minute in relation to the areas charged at a specified rate are also indicated at the foot of FIG. 4.

The charge thrower 1 may be operated in a fixed position or oscillated horizontally from side to side. The thrower 1 may be provided with a motorized chain drive (not shown) which is adapted to continuously swing it back and forth at a constant speed through a horizontal arc with a pivot or work point just inside the feeding port of the furnace or reactor. The are of travel and the sector of travel are controlled by drive maximum (or outer) limit switches (not shown) with locational adjustment. The oscillating drive unit is actuated from a switchbox (not shown) separate from the charge thrower speed control.

When the thrower l is oscillating, its swing is electrically interlocked with the belt speed program in order to prevent the charge stream from hitting the walls of the reactor. An inner limit switch 12 is mounted before the right drive limit switch. However, a similar inner limit switch 12 is not necessary before the left drive limit switch if the line of throw is parallel tothe longitudinal axis of the reactor at the left limit drive. As the thrower swings to the right, it activates inner limit switch 12 causing the thrower to decelerate (if it is not already in a decelerate period). The thrower 1 will continue to decelerate, and if the low speed limit is reached, will continue to operate at the low speed limit, until it has swung to the end of its arc of travel, has reversed, and again passes inner limit switch 12 causing deactivation thereof. The thrower 1 is then automatically accelerated and resumes normal operation.

When the charge thrower l is operated from a fixed position at a fixed belt speed the charge falls in a small, roughly elliptical area of the bath surface. The charge distribution in this area can be represented by a charge distribution curve (in units of lb./ft. /min.) along an axis coincident with the centre line of the charge thrower belt as can be seen from the fixed low belt speed distribution in FIG. 2. If the belt speed is increased, the charge area moves further away from the thrower 1, and at the same time the charge distribution curve becomes lower and broader. This is also shown schematically in FIG. 2.

The charge thrower speed control is used to program the belt speed of the thrower 1 so that the charge is distributed more uniformly and over a larger area along the line of throw than is possible at a fixed belt speed. The programming involves three parameters: the low speed limit, the high speed limit, and the delay time. As the low speed is decreased the area of distribution covers an area closer to the thrower 1 than with the high speed operation. A practical lower limit may be imposed by the manner in which the sill of the reactor charge port interferes with the charge stream from the thrower. As the belt speed is increased the area of distribution an area more remote from the thrower l. A practical upper limit is imposed in that with the use of overly excessive belt speeds charge may fall beyond the smelting zone in the reactor or alternatively charge may impinge directly on the reactor wall which is an undesirable feature. Since the rate of charging per unit area is less at the high speed, the delay time should be sufficiently long that the amount of charge at opposite ends of the reactor is approximately the same.

The maximum high speed limit is set by the maximum speed of the thrower motor and the ratio of the drive pulleys. The minimum high speed limit varies with the low speed limit and is based on the characteristics of the electronic circuit of the control and the results of tests with the charge thrower l on a simulated reactor.

The effect of programming the belt speed on the I charge distribution obtained with the thrower l operating from a fixed position is shown schematically in FIG. 3. Programming the thrower belt speed has little effect on the lateral distribution of charge. In order to improve the lateral distribution of the charge the thrower 1 is oscillated. A directional change in throw may then be superimposed on the trajectory of the charge which is controlled by the belt speed program. The speed of the oscillating drive unit is fixed, but the arc of travel and the sector of travel can be varied by adjusting the position of the drive limit switches. The maximum position of the left drive limit switch should preferably be set such that when the thrower 1 is at the end of its arc of travel, the line of throw is parallel to the longitudinal axis of the reactor in order to avoid impingement of the charge on the reactor wall. The maximum position of the right drive limit switch is determined by charge impingement on the side of the reactor feed port. The

purpose of the limit switch 12 which is placed before the right drive limit switch in the charge thrower control system, is to prevent or inhibit charge impingement on the left reactor wall (when viewed from the charging end) by decelerating the thrower 1 whenever limit switch 12 is activated. The charge distribution obtained with oscillation of the thrower 1 is shown schematically in FIG. 4 as previously indicated.

In the operation of the thrower speed control circuit shown in FIG. 4 all electrical connections (106 to 116) to the speed control are made through an amphenol connector. Power for the control is fed from a 1 volt, 6O cycle line connected to terminals 113 and 114 through switch 17 (the automatic control-manual control switch) and a 0.5 amp fuse 45, to the transformers l8 and 19. Transformer l8 converts the voltage to 12 volts and this voltage is then rectified by two half-wave diode rectifiers 20, a. One of the diodes 20 supplies a Zener diode voltage stabilizer 21. The accuracy of the delay period controlled through the program timer depends on output C of the stabilizer 21. The diode 20a supplies dc current to the differential relay circuit which consists of two identical halves each embodying a relay 33, 42 operated by a silicon controlled rectifier 34, 34a.

Transformer 19 supplies a 12 volt a.c. output which is electrically isolated from the secondary of transformer l3 and which is rectified by a bridge rectifier 23. The output of the rectifier 23 is filtered, and then stabilized at 12 volts with a Zener diode 24. Two potentiometers 25' are connected across the stabilized 12 volt d.c. output and are used to set the high and low speed limits and apply a corresponding reference voltage to the differential relay circuits.

Terminals 106 and 107 are connected to the tachometer generator 5. The a.c. tachometer voltage is recti' fied by bridge rectifier 26 and filtered by capacitor 27. The resulting dc. voltage, which is a function of the thrower belt speed, is measured with a voltmeter 28 calibrated in feet per second. A voltage divider chain consisting of a potentiometer 29 and a resistor 30 attenuates the voltage up to a maximum of 12 volts.

As the thrower accelerates or decelerates, the tachometer voltage increases or decreases and an increasing or decreasing voltage is applied by the voltage divider chain to the left end of the differential relay circuit (relay 42 side). A reference (from 0-12 volts) voltage is applied to the right half of the differential relay circuit by one of the two potentiometers 25, 25 through contacts 37-1, 37-3 respectively of a relay 37 to be disclosed later. If the tachometer voltage is lower than the reference voltage, SCR rectifier 34 is rendered conductive and relay 33 is energized by the rectifier 34. Powerstat servo motor SM is thus energized through connection 1 11, normally closed contacts 42-] of relay 42, now closed contacts 33-1 of relay 33 and connection to cause the thrower to accelerate until the voltage across both sides of the differential relay is balanced.

The program timer contains a SCR rectifier 35 connected to relay 37. A NPN transistor 41 is connected in the gate circuit of the rectifier to raise the input impedance thereof. When transistor 41 is not conducting, a positive potential is applied to the gate of the rectifier 35 and the rectifier energizes relay 37. When relay 37 is energized, high speed potentiometer 25 is connected to the differential relay circuit through contacts 37-1 and the differential relay circuit is switched to accelerate by energizing relay 33.

When the thrower reaches the preset high speed limit, the tachometer voltage becomes equal to the voltage of the potentiometer 25 and the SCR rectifier 34 is rendered non conductive. Relay 33 is then released and contacts 33-2 thereof are closed to start the delay period through the circuit including potential source C, connection 109, the normally closed contacts of limit switch 47, connection 108, closed contacts 33-2, rotary switch ROT, resistor 38, capacitor 39, and terminal B of the source. The length of the delay period is controlled by resistors 38 which determine the time required to charge capacitor 39 to a predetermined value. The resistors 38 in the timing circuit can be changed by turning out a switch ROT so as to preset the delay period. When the capacitor 39 is charged to its predetermined value, a Zener diode 40 starts to conduct and supplies a positive potential to the base of transistor 41. The transistor 41 then conducts, shunts the input of the rectifier 35 and causes relay 37 to open, thus ending the delay period.

Contacts 37-2 are thus closed and Zener diode 40 is short circuited so as to permit capacitor 39 to slowly discharge through the base-emitter circuit of transistor 41 and maintain the transistor conductive during all the deceleration period of the motor.

The release of relay 37 causes the closure of contacts 37-3 and the low speed reference voltage 25' is then applied to the right side of the differential relay. The tachometer voltage then becomes higher than the reference voltage and SCR 34a becomes conductive. The deceleration relay 42 is activated causing the closure of contacts 42-2 and the powerstat servo-motor to rotate in the reverse direction to cause the thrower 1 to slow down. When the pre-set low speed limit is reached, the differential relay 42 opens to stop deceleration of the thrower.

As the relay opens a If capacitor 43, which was previously charged from potential source C through contacts 42-3, discharges through the gate of a silicon controlled rectifier 44 connected in parallel across the condenser 39 of the timer. This impulse discharges the condenser, and relay 37 is again energized starting a new cycle.

When the charge thrower l is operated with the oscillating drive unit a limitswitch 47 comes into play. Activation of the limit switch causes a 12 volt positive potential originating from terminal C through connections 109 and 1 to be applied to the base of transistor 41 through a resistor 46. The transistor 41 conducts, shunts the gate of the silicon controlled rectifier 35 and causes relay 37 to open. The deceleration side relay 33 of the differential relay is activated, and the charge thrower decelerates. If the limit switch 47 is closed for a sufficiently long time period, the charge thrower will reach the low speed limit, and will continue to operate at the low speed limit as relay 37 cannot close as long as the limit switch 47 is activated. When the limit switch 47 is deactivated, relay 37 is closed, starting a normal cycle. Zener diode 48 is provided for preventing the potential from being applied to the transistor 41 when the limit switch is operated from charging capacitor 39.

The two components 42 and the two components 33 in the circuit diagram are each in fact the same. In one case components 33 and 42 are marked with the symbols for relay coils, and in the other case the actual contacts are shown with the symbols beside them, i.e., the symbols refer to the contacts within the dashed lines. Relay 33 is also provided with contacts 33-3 and 33-4 which activate pilot lights 49 and 50 to indicate when the acceleration and delay periods occur while relay 42 is provided with contacts 42-4 to activate pilot light 51 to indicate when deceleration occurs. The circuit diagram is, of course, intended as an explanatory diagram to assist persons working with the equipment of the present invention.

The servo motor SM is also provided with manually operated contacts 52 which permit independent control of the setting of powerstat 3.

FIG. 1 shows a powerstat 3 driven by a servomotor 4. in the experimental work on the present invention the servomotor speed was low (24 RPM) with the result that the thrower motor speed followed the powerstat settings without any significant lag.

An alternative method of controlling the speed of the thrower motor envisages the use of a silicon controlled rectifier and with this alternative, the voltage level of 0-5 volt d.c. controls the conduction angle of the silicon control rectifier. Acceleration and deceleration are achieved by charging and discharging a capacitor through a constant current source. The capacitor provides the 05 volt d.c. control voltage through a high impedance voltage follower. Setting of the charging or discharging rate on the programmer varied the acceleration and deceleration rate.

A d.c. motor was used in the experimental work; however, any suitable motor can be used which provides the necessary torque at various speeds.

It is not necessary for the material or charge fed to the thrower l to be in any particular or critical form. The charge thrower 1 has been used successfully to feed a variety of forms and content of charge material including copper concentrate pellets, a mixture of pellets and silica flux, and a mixture of unagglomerated copper concentrate and silica flux. The size of the pellets and of the flux has ranged from 1/4 inch to 1 inch. Tests in the laboratory showed that the initial velocity imparted to copper concentrate pellets was essentially independent of the pellet size at a given thrower belt speed. In practice, a large moving mass or stream of pellets and flux issues from the charge thrower l. The particles in this stream are subject to interaction and collision, and the effect of air resistance on individual particles of different sizes is not likely to be observed. Any change in the charge distribution pattern caused by a change in the average particle size of the charge can be corrected with the charge thrower control.

it is clear that this development represents a distinct advance in the art of automatically feeding charge material into a furnace or reactor and will provide benefits and advantages to the industry as a whole.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for controlling the distribution of material into a vessel comprising:

a. an endless belt thrower constructed and dimensioned to convey said material and feed it into said vessel in a predetermined manner;

b. a variable speed motor adapted to drive said thrower;

c. a control system adapted to regulate the voltage of said thrower and the speed at which said motor drives said thrower;

d. voltage generating means for producing a voltage proportional to the speed of said motor; and

e. a program system for generating reference voltages corresponding to at least two predetermined speeds of operation of said motor and for comparing said voltages with the voltage produced by said voltage generating means for operating said control system accordingly.

2. An apparatus as defined in claim 1, wherein said voltage generating means is a tachometer generator coupled to said motor, and wherein said program system includes an upper and a lower reference voltage supply, a differential relay circuit including two separate relays connected to said tachometer generator, and means for successively connecting said upper and lower reference voltage supply to said differential relay to cause the said first or second relay respectively to operate said control system so as to successively increase and decrease the speed of said motor.

3. An apparatus as claimed in claim 2, wherein said control system includes a powerstat having a movable tap adapted to provide a variable voltage to said motor and a servo motor responsive to said first or second relay for moving said tap in one direction or the other respectively so as to increase or decrease the voltage applied to said motor.

4. An apparatus as claimed in claim 3, wherein said means for connecting said upper and lower reference voltage supply is a third relay which operates a first set of normally open contacts connecting said high speed reference voltage to said differential relay circuit to operate said first relay, and a second set of normally closed contacts connecting said low speed reference voltage to said differential relay circuit to operate said second relay.

5. An apparatus as claimed in claim 4, further comprising means for initially energizing said third relay so as to first connect said high speed reference voltage to said differential relay circuit and so cause the motor to increase its speed up to its maximum value and for subsequently deenergizing said third relay so as to connect said low speed reference voltage to said differential relay circuit in order to cause the motor to decrease its speed down to its minimum value.

6. An apparatus as claimed in claim 5, wherein said means for energizing said third relay comprises a SCR rectifier connected in series with said relay and a normally non-conductive transistor for biassing said rectifier into conduction, and wherein said means for deenergizing said third relay comprises means for rendering said transistor conductive so as to release said third relay.

7. An apparatus as claimed in claim 6, wherein the acceleration and deceleration periods of said motor are separated by a predetermined time delay wherein the motor is maintained at its high speed, and further comprising a timer for rendering said transistor conductive after said predetermined time delay.

8. An apparatus as claimed in claim 7, wherein said timer includes a capacitor which is energized through a normally closed contact of said first relay when released and a Zener diode interconnecting said capacitor to said transistor and which is rendered conductive when the voltage across said capacitor has reached a predetermined value.

9. An apparatus as claimed in claim 8, further comprising means for discharging said capacitor when said second relay is released so as to render said transistor non conductive and thus restore the rectifier into a conductive state.

10. An apparatus as claimed in claim 7, wherein said apparatus is further provided with an oscillating drive unit adapted to oscillate said thrower horizontally and with a pair of outer limit switches adapted to control the horizontal oscillation of said thrower, and further comprising at least one inner limit switch actuated by said thrower before the oscillating movement thereof reaches the outer limit switch for rendering said transistor conductive so as to release said third relay and thus connect said low speed reference voltage to said differential relay in order to reduce the speed of said motor and prevent the material fed into the furnace from striking the walls of the furnace.

11. Apparatus for the controlled feeding of material into a vessel including:

a. an endless belt thrower constructed and dimensioned to convey said material and feed it into said vessel in a predetermined manner,

b. a variable speed motor adapted to drive said thrower,

c. a first control system adapted to regulate the voltage of said motor and the speed at which said motor drives said thrower,

d. a program system adapted to regulate said control system according to a predetermined program,

e. an oscillating drive unit adapted to oscillate said endless belt thrower horizontally in a controlled manner, and

f. a second control system separate from said first control system for actuating said oscillating drive unit. a

12. The apparatus as claimed in claim 11, wherein a pair of outer limit switches is adapted to control the horizontal oscillation of said thrower.

13. The apparatus as claimed in claim 12 including an inner limit switch which is adapted to be interlocked with the speed control and program system so as to reduce the speed of said thrower and inhibit the material fed into the furnace from striking the walls thereof.

14. The apparatus as claimed in claim 12 in which said thrower is constructed and driven in such a way that the material charged into said vessel has a line of throw parallel to the longitudinal axis thereof when said thrower reaches one of said outer limit switches.

15. The apparatus as claimed in claim 14 wherein said thrower activates an inner limit switch which is interlocked with the speed control and program system before the thrower reaches the other of said outer limit switches.

16. The apparatus as claimed in claim 15 wherein the inner limit switches which are interlocked with the speed control and program system are activated by said thrower before the oscillating movement of said thrower reaches the outer limit switches.

17. The apparatus as claimed in claim 15 wherein the activation of said outer limit switches results in said thrower reversing its horizontal oscillation. 

1. Apparatus for controlling the distribution of material into a vessel comprising: a. an endless belt thrower constructed and dimensioned to convey said material and feed it into said vessel in a predetermined manner; b. a variable speed motor adapted to drive said thrower; c. a control system adapted to regulate the voltage of said thrower and the speed at which said motor drives said thrower; d. voltage generating means for producing a voltage proportional to the speed of said motor; and e. a program system for generating reference voltages corresponding to at least two predetermined speeds of operation of said motor and for comparing said voltages with the voltage produced by said voltage generating means for operating said control system accordingly.
 2. An apparatus as defined in claim 1, wherein said voltage generating means is a tachometer generator coupled to said motor, and wherein said program system includes an upper and a lower reference voltage supply, a differential relay circuit including two separate relays connected to said tachometer generator, and means for successively connecting said upper and lower reference voltage supply to said differential relay to cause the said first or second relay respectively to operate said control system so as to successively increase and decrease the speed of said motor.
 3. An apparatus as claimed in claim 2, wherein said control system includes a powerstat having a movable tap adapted to provide a variable voltage to said motor and a servo motor responsive to said first or second relay for moving said tap in one direction or the other respectively so as to increase or decrease the voltage applied to said motor.
 4. An apparatus as claimed in claim 3, wherein said means for connecting said upper and lower reference voltage supply is a third relay which operates a first set of normally open contacts connecting said high speed reference voltage to said differential relay circuit to operate said first relay, and a second set of normally closed contacts connecting said low speed reference voltage to said differential relay circuit to operate said second relay.
 5. An apparatus as claimed in claim 4, further comprising means for initially energizing said third relay so as to first connect said high speed reference voltage to said differential relay circuit and so cause the motor to increase its speed up to its maximum value and for subsequently deenergizing said third relay so as to connect said low speed reference voltage to said differential relay circuit in order to cause the motor to decrease its speed down to its minimum value.
 6. An apparatus as claimed in claim 5, wherein said means for energizing said third relay comprises a SCR rectifier connected in series with said relay and a normally non-conductive transistor for biassing said rectifier into conduction, and wherein said means for deenergizing said third relay comprises means for rendering said transistor conductive so as to release said third relay.
 7. An apparatus as claimed in claim 6, wherein the acceleration and deceleration periods of said motor are separated by a predetermined time delay wherein the motor is maintained at its high speed, and further comprising a timer for rendering said transistor conductive after said predetermined time delay.
 8. An apparatus as claimed in claim 7, wherein said timer includes a capacitor which is energized through a normally closed contact of said first relay when released and a Zener diode interconnecting said capacitor to said transistor and which is rendered conductive when the voltage across said capacitor has reached a predetermined value.
 9. An apparatus as claimed in claim 8, further comprising means for discharging said capacitor when said second relay is released so as to render said transistor non conductive and thus restore the rectifier into a conductive state.
 10. An apparatus as claimed in claim 7, wherein said apparatus is further provided with an oscillating drive unit adapted to oscillate said thrower horizontally and with a pair of outer limit switches adapted to control the horizontal oscillation of said thrower, and further comprising at least one inner limit switch actuated by said thrower before the oscillating movement thereof reaches the outer limit switch for rendering said transistor conductive so as to release said third relay and thus connect said low speed reference voltage to said differential relay in order to reduce the speed of said motor and prevent the material fed into the furnace from striking the walls of the furnace.
 11. Apparatus for the controlled feeding of material into a vessel including: a. an endless belt thrower constructed and dimensioned to convey said material and feed it into said vessel in a predetermined manner, b. a variable speed motor adapted to drive said thrower, c. a first control system adapted to regulate the voltage of said motor and the speed at which said motor drives said thrower, d. a program system adapted to regulate said control system according to a predetermined program, e. an oscillating drive unit adapted to oscillate said endless belt thrower horizontally in a controlled manner, and f. a second control system separate from said first control system for actuating said oscillating drive unit.
 12. The apparatus as claimed in claim 11, wherein a pair of outer limit switches is adapted to control the horizontal oscillation of said thrower.
 13. The apparatus as claimed in claim 12 including an inner limit switch which is adapted to be interlocked with the speed control and program system so as to reduce the speed of said thrower and inhibit the material fed into the furnace from striking the walls thereof.
 14. The apparatus as claimed in claim 12 in which said thrower is constructed and driven in such a way that the material charged into said vessel has a line of throw parallel to the longitudinal axis thereof when said thrower reaches one of said outer limit switches.
 15. The apparatus as claimed in claim 14 wherein said thrower activates an inner limit switch which is interlocked with the speed control and program system before the thrower reaches the other of said outer limit switches.
 16. The apparatus as claimed in claim 15 wherein the inner limit switches which are interlocked with the speed control and program system are activated by said thrower before the oscillating movement of said thrower reaches the outer limit switches.
 17. The apparatus as claimed in claim 15 wherein the activation of said outer limit switches results in said thrower reversing its horizontal oscillation. 